Actuator with progressive gear

Abstract

An actuator for a grille shutter assembly of a vehicle has a motor connected to an output via a gear train. The output has a connection for connecting to louvers of the grille shutter assembly. The gear train has a gear ratio which is variable depending on the actuation angle of the output shaft. Optionally, a return spring is arranged to resiliently return the output shaft to an initial actuation angle when the motor is not active.

The invention claimed is: 
     
       1. An actuator for a grille shutter assembly of a vehicle, comprising:
 a motor having a motor shaft; 
 an output, including an output shaft and a connection for connecting to louvers of the grille shutter assembly; and 
 a gear train connecting the motor shaft to the output shaft, 
 characterized in that the gear train has a gear ratio that is variable depending on a varied actuation angle of the output shaft; and 
 wherein the gear train comprises a first spiral gear wheel and a second spiral gear wheel in mesh with the first spiral gear wheel. 
 
     
     
       2. The actuator of  claim 1 , wherein the second spiral gear wheel is fixed to the output shaft. 
     
     
       3. The actuator of  claim 1 , wherein the first spiral gear wheel is connected to the motor shaft by at least one spur gear. 
     
     
       4. The actuator of  claim 1 , wherein the first and second spiral gear wheels have logarithmic pitch paths. 
     
     
       5. The actuator of  claim 1 , further comprising a return spring arranged to resiliently return the output shaft to an initial actuation angle when the motor is not active. 
     
     
       6. The actuator of  claim 5 , wherein the return spring is a coil spring disposed about the output shaft with one end fixed to the second spiral gear wheel and a second end fixed to a part supporting the output shaft. 
     
     
       7. The actuator of  claim 1 , wherein the motor is a stepper motor and is connected to a printed circuit board (PCB) having a control circuit for controlling the motor in response to control signals. 
     
     
       8. The actuator of  claim 1 , wherein the output comprises two output shafts. 
     
     
       9. A grille shutter assembly for a vehicle, comprising a frame; wherein the louvers include at least one set of louvers pivotably connected to the frame and the actuator of  claim 1 , the actuator being arranged to pivotably adjust the orientation of the louvers with respect to the frame. 
     
     
       10. The grille shutter assembly of  claim 9 , wherein the output shaft has a non-round socket in an end thereof and the louvers are pivotably adjusted by an actuation shaft that has an end received in the socket. 
     
     
       11. The grille assembly of  claim 10 , wherein the non-round socket is substantially star shaped.